Rotary magnetic switch



Feb, 6, 1951 H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 1 Feb. 6, 1951H. E. SCHLEICHER ROTARY MAGNETIC SWITCH 7 Sheets-Sheet 2 Filed Nov. 26,1943 Feb. 6, 1951 H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 5 Feb. 6, 1951H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC swITcH Filed Nov. 26, 1945 7 Sheets-Sheet 4 Feb. 6, 1951H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC SWITCH Filed Noll. 26, 1945 7 Sheets-Sheet 5 al a5x4445140 Feb. 6, 1951 H. E. SCHLEICHER 2,540,294

RDTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 6 i a; avliliiefiiilm A L52 V 50 Feb. 6, 1951 H. E. SCHLEICHER 4 2,540,294

ROTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 7 PatentedFeb. 6, 1951 aoranr menarrc swrrcn Harold E. Schleicher, West Hartford,Conn., as-

signor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., acorporation of Connecticut Application November 26, 1943, Serial No.511,855

25 Claims. 1

This invention relates to electromagneticallyoperated circuit makers andbreakers capable of operation locally, or b remote control if desired,and having provision for automatic overload operation incorporated intothe switch.

Modern battle conditions require electrical control apparatus towithstand high impact shocks, the shock test requirements havingrecently been increased more than tenfold. Attempts heretofore to meetthe test requirements involved the addition of counterweights, inertia.hammers, special brush-type contacts, etc., to existing conventionalcommercial structures. These have proved unsatisfactory under the newrequire-- ments. A new approach to the problem was needed to produce ascientifically designed device in which the movable parts would bedynamically and statically balanced.

It is an object of the present invent on to provide anelectromagnetically-operated circuit maker and breaker designed towithstand high impact tests by providing for dynamic and static balanceof its movable parts. A related object is to provide an improved designof electromagnetic circuit maker and breaker requiring a mini mum amountof energy to produce initial and succeeding movement and to maintain themechanism in closed position.

Another object is to provide an improved electromagnetic switchstructure which can be mounted in any position without entailingincreased energy consumption in its operation to overcome gravity, heavybiasing springs, or the like, and which requires less energy under anyconditions than prior devices for similar usage.

Another object is to provide an electromagnetic switch of the above typewhich will have a more Other objects of the invention will becomeapparent as the invention is described in connection with the drawings.

Although useful in military fields because of its peculiar advantages,the invention is nevertheless useful in a wide variety of domesticsituations.

In the drawings Fig. 1 is a perspective view of a device embodying theinvention;

Fig. 2 is a side elevation view of the device of Fig. 1;

Fig. 3 is an exploded perspective view of certain parts employed in thedevice of Figs. 1 and 2;

Fig. 4 is an elevational section view taken alon line 4-4 of Fig. 2;

Fig. 5 is a plan view of the electromagnetic structure which is locatedwithin the forward uniform pull on its armature, a higher sealing pull,with quieter operation and less wattage loss in alternating current use.

Another object is to provide an electromagnetic switch of the above typefor the use of dual magnet coils to enable, optionally, the use of thedevice on difl'erent voltages.

Another object is to provide for remote or local manual control of thedevice.

Another object is to provide overload protection for a device of theabove type, in which the shock-proof features are embodied and in whichthe principles of dynamic balance are observed and incorporated, notonly to preserve the effectiveness of the incorporation of the sameprinciple in the other parts of the device, but also to insure operationaccurately and only at the time and under certain predeterminedconditions.

end of the device in Fig. l, the housing being removed;

Fig. 6 is a vertical section view taken along line 66 of Fig. 4;

Fig. '7 is an exploded perspective view of'certain parts of theelectromagnetic structure;

Fig. 8 is an elevational section view taken along line 8-8 of Fig. 2,showing the details of'auxiliary switch for the holding-circuit and itsmanual operating means;

Fig. 9 is an exploded perspective view of the bridging contact of theholding circuit auxiliary switch;

Fig. 10 is a horizontal section view of the mechanism of Fig. 8, takenalong line Ill-l0 of Fig.

Fig. 11 is an elevational detail view of the spring-biasing structureassociated with the main shaft;

Fig. 12 is a section view of the spring-biasing structure, taken alongline l2-l2 of Fig. 11;

Fig. 13 is an elevational section view taken along line l3--l3 of Fig. 2and illustrating one set of the line contacts;

Fig. 13a is a fragmentary detail of the line contact mounting structure;

Fig. 13b is a section view taken along line l3b-i3b of Fig. 13a;

Fig. 14 is an exploded perspective view of the main-line bridgingcontact assembly; v

Fig. 15 is an elevational section view, taken along line l5l5 of Fig. 2,of the section of the device containing the overload protective devices;

Fig. 16 is a view similar to Fig. 15 but with the heater coils and fixedcontrol contacts removed;

Fig. 17 is a section view taken transversely along line |'|-l 1 of Fig.15, of the portion of the invention illustrated in Fig.

Fig. 18 is a section view taken along line |8-.|8 of Fig. 15;

Fig. 19 is a section view taken along line Ill-I9 of Fig. 15;

Fig. 20 is an elevational section view taken along line 2|J-2|J of Fig.2 and shows the opposite side of the section of the device illustratedin Fig. 15;

Fig. 21 is a view similar to Fig. 20, with some of the tripping-mechanism and its resetting means removed;

Fig. 22 is a detail view showing in elevation tripping mechanism thatwas removed from Fig. 20;

Fig. 23 is an exploded perspective view of the tripping mechanism ofFig. 22; and

Fig, 24 is a wiring diagram illustrating connections for a two-coil formof electromagnet and a common three wire form of contact arrangement,such as that illustrated in the preceding figures.

Referring to the drawings, the main switch contacts, certain controlcircuit contacts and electromagnetic operating mechanism therefor arehoused within a cylindrical sectional casing, built up from moldedinsulating discs 60, I02, I08, H2, I22, |3O and a metal shell 34, all ofwhich are ultimately supported from a base plate 30 by means of themounting plates 3| and 32 bolted on said base plate and extending atright angles to the face thereof. The immediate support for the casingsections is four spaced parallel rods 36, 31, 38, 39 (Figs. 2, 3 andothers), running between and supported by mounting plates 3|, 32. Holesare formed in each of the parts that make up the casing so they may heslid on the rods.

The device may be conveniently considered as 3 comprising a number ofsections or units. Referring to Fig. 2, in the section A at the left endis the electromagnetic operating means, the electric tenninalconnections for which extend through the left end cover or cap plate 33,which may conveniently be made of molded insulating material and securedagainst the face of the mounting plate 3| by screw bolts.

In the section B are a switch and its manual operating means for localcontrol of operation of the device.

In the sections C, D and E are the main circuit making and breakingcontacts for the three lines of a three-wire power system. However, theinvention is applicable equally to the making and breaking of any numberof lines, the three line form having been chosen for illustration as apreferred embodiment because of its common usage. Each section includesa pair of fixed contacts and a movable bridging contact structure,hereinafter more fully described.

In section F are located the overload protective devices which, in theform illustrated, are for a three-wire line.

The movable bridging contact structure and the movable portion of theelectromagnetic operating mechanism are mounted upon a main shaft 40(Figs. 3, 4, 6 and others) whose axis is the main axis of the device.The main shaft 40 has its end journalled in and supported by themounting plates 3| and 32.

The electromagnetic operating means The parts of the electromagneticoperating means are protected by and located within a twopart magneticsheet metal housing (Figs. 1, 2, 6). One part 34 has a cylindrical walland an integral end wall. The other part '35 is a sheet metal disccompletely covering the open end of the part 34. The end wall of part 34lies against the mounting plate 3| and both end wall and cover plate 35are apertured centrally for passage of the main shaft. Louvers 3421 forventilation may be formed in the cylindrical wall of part 3. As willpresently appear, the housing 34, 35 completely surrounds theelectromagnetic parts and is in close proximity thereto, providing aflux path around the coil sides.

Referring particularly to Figs. 3, 4 and 7, it will be observed that thelaminated armature 50 of the electromagnet is substantially of Z-shape,with the oppositely directed ends of its arms 50a, 5% made arcuate. Asquare passageway is formed through the central portion of the armatureto enable it to be slid upon and to turn with the main shaft 40, which,also, is square in section. The nature of the armature structure is suchthat the armature is dynamically balanced upon the main shaft, so thatit possesses dynamic and static equilibrium at all times, eliminating,for all practical considerations, tendency for the armature and shaft toturn, unless acted on by an outside force.

The curved end portions 50a, 50b of the armature are adapted to move inand out of hollow toroidal solenoid coils 52, 53 positioneddiametrically opposite each other about the main shaft 40. These coilsmay be connected electrically either in series or in parallel. In caseof use, for example, on a 220-volt 3-wire line, if the coils are each-volt coils they may be connected in series across the 220-volt lines;or they may be connected in parallel between the neutral and one outsideline, supplying 110 volts. Alternatively, the coils may have dualwindings, each winding comprising a 110-volt coil which may be connectedin series or in parallel with its neighbor, in a manner similar to thatjust described, and in series or parallel with the opposite dual coil.In any case, the electromagnetic effect of the coils will be cumulative,creating a greater force and a more uniform pull on the armature than asingle coil.

Cooperating with the coils 52 and 53 are pole pieces (designated as awhole by 54 and 56) made up of laminated magnetic material. These polepieces are identical and are generally arcuate in form, being enlargednear one end as at 54a and having an arcuate extension such as cconcentric with, but of less radius than, the main portion of the polepiece. The extensions 54c and 560 extend into one end of each of thecoils 52 and 53, while the main portions of the pole pieces bridge theair gap between the ends of the coils 52 and 53, said portions lyingjust beyond but closely adjacent the paths of movement of the arcuateportions 50a and 50b of the armature. Lying against the inner face ofthe pole pieces are non-magnetic shield or liner members 55 and 51.These shield members are channelled in shape and arcuate in form to fitaround the inner and side faces of the pole piece which they shield.They may be aflixed to the pole pieces by riveting. A tongue, such as55a, is bent inwardly toward the axis of the armature adjacent one endof each shield member, so as to lie along the inclined surface of theenlargement 54a of the pole piece. When the armature is returned toinactive position by a spring, as hereinafter described, upondeenergization of the coil of the magnet the back side of its radialarms will abut the tongue 55a, preventing the armture from sticking tothe pole piece. The liners also provide a momentary time delay, whilethe flux field is building up to strength needed for moving thearmature. This and the non-sticking feature insure that the initial pullon the armature will be unopposed by the armature itself.

To fix the pole pieces and the coil in position resiliently, circularapertures, such as 54p, are provided in the arcuate portions of the polepieces to enable the pole pieces to be mounted on the mounting rods36-39, inclusive. As illustrated, the pole piece 56 is mounted upon therods 36 and Il. To position or space the pole pieces, small coiledcompression springs 58 are mounted on the rods, between the pole piecesand the inner surface of that portion of the housing which lies againstthe plate 3|; and on the opposite side of the pole piece, similar smallcompression springs 58 (also mounted upon the mounting rods) lie betweenthe pole pieces and the next adjacent section B.

' To allow limited, but to prevent excessive, side thrust of the polepieces, stud pins such as 548, are attached to the opposite side facesthereof and are engageable with the side walls of the enclosure in whichthe magnet is housed.

From the foregoing, it may be observed that as the coils are energized,a magnetic field will be set up and will be concentrated at the ends ofthe coils in the pole pieces and concentrated in the oscillatory path ofthe armature, reducing losses to a minimum. The force of the magneticfield will draw the arcuate portion of the armature into the coil andagainst the faces 54d, 56d of the extensions 54c, 580. (These faces mayconveniently be provided with shading coils in the conventional manner.)Upon deenergization of the coils, the armature will be retracted to itsoriginal po:ition by spring means hereinaiterto be described. Theoscillatory movement of the armature is communicated to the main shaftof the device because the shaft is of the square section. An insulatingsleeve M is provided to insulate the shaft from all the parts itcarries.

To return the shaft 40 to the position normally occupied when theelectromagnet is deenergized, a fiat coil spring 42 (Fig. 3) is placedaround the end of the shaft near mounting plate 32, between v aspring-tension and stop member 44- and an anchor member 45. The stop andspring tensioning member is a small sheet metal stamping of irregularshape (see Fig. 3) with a square aperture for the square main shaft 40and spaced, laterally-bent, radially-extending stop lugs a which areadapted to butt against a circular stud or pin 46 extending from themounting plate 32 as the shaft 40 oscillates. On the opposite side ofthe member at its periphery is a spring tensioning lug 44c bcnt normalto the member and embraced by the ends of the coil spring 42. Alsoembraced by these coil spring ends is a similar lug 450 on thestationary anchor member 45. The anchor member 45 is a small sheet metaldisc-shaped stamping with a keyhole aperture which interengages with acircumferential groove 409 in the end of the shaft 40 to hold the shaftagainst axial movement but permit its rotation when the anchor member isfixedly secured within a countersunk recess 32r in the mounting plate32.

The stop plate or member 44 has its travel limited in both open andclosed contact positions. The stoppage in the closed position enablesthe 6 armature and magnets to align themselves freely: otherwise themagnets would be forced against the mounting rods and prevented fromassuming natural adjustment.

The foregoing electromagnet structure is also described and is claimedin my divisional application Serial No. 185,422 filed September 18,1950.

The local control contacts and their operating mechanism In customarypractice, the control of the electromagnet is usually accomplished by apush button station that often is remote from the magnet itself.However, in some fields of use, it is desirable that the device bemanually operable locally. To meet such a demand, a local control isprovided for in the present invention in the section B of the device.

My invention, without preventing the use of conventional remote controlbuttons, provides for local control manually by utilizing, as controlcontacts and in a reconstructed and novelly-improved and manuallyoperable arrangement, the contacts in the conventional sealing-incircuit. In normal manual local operation, these control contacts notonly seal-in the main contacts, but these control contacts form theprimary circuitclosing means for bringing about energization of theelectromagnet coil.

If, however, it is desired to use the invention in a remote controlcircuit arrangement, the dual functioning sealing-in and controlcontacts can be utilized for their sealing-in function after theenergization of the solenoid; and the provision of the supplementaryremote control can be made without affecting the operability of thelocal control arrangements.

The current carrying parts, except the terminals, are housed whollywithin insulating discs 60, which are recessed for the stationary andmovable contacts and for the mechanism by which the contacts are or maybe manually manipulated. The discs 60 and. the similar purpose discs forthe remaining sections hereinafter described are all mounted on the rods3639 by sliding the rods through suitable apertures Bilr in the discs.

Two identical stationary contacts, designated generally by the numerals62, 64, are irregular, stamped, sheet metal parts. From a circular,central portion having a screw-threaded aperture, there extends anarcuate arm, such as 622), whose end turns at right angles inwardlytoward the axis of the device, as 620, to form a contact blade. From thecircular central portion of the contact member, in a positionsubstantially degrees from the position of extension of the arm 62b,there extends another arm 62d Wl'ZOSe end portion 62a is bent at rightangles to arm 62d to form a wire terminal. The portions 622) and d,lying in one plane, are countersunk within a re cess molded within thebase of the insulating mounting disc 60. A contact and terminal member64, identical to contact 62, lies in a diametrically opposite positionon the disc 60.

The contacts 62 and 64 are adapted to be engaged and disengaged bymovable bridging contact structure made up of the parts clearly shown inthe exploded view of Fig. 9. This movable contact structure comprises apair of identical stamped sheet metal, highly-conductive members 66 of aform illustrated in Fig. 9, namely having a large central circularsection with a large circular central aperture and with a pair ofdiametrically oppositely-extending resilient arms forming contact blades66c. Within the circular apertures of the members 66 lies a cylindricalcollar 61 having four lugs 61a extending from the edges thereof on eachside of the collar and adapted to be received within apertures providedin a pair of disc-shaped spring-tensioning drivin; members 68, 69, whichlie against the opposite outslde faces of the conductive members 66.

The ends of the lugs 61a are peensd over to permanently hold the springtensioning members and the conductive members 66 together as a unit.Coiled around the collar 67 and located between the conductive members66 is a coil spring 10, whose ends are radially outturned to engage theend portions of arms 68a, 69a radially extending from the springtensioning members 68 and 69. The arms are so located on the springtensioning members 68 and 69 that when these members are securedtogether by the peening over of the end of the collar 61, theradially-extending arms will lie side by side, covering an arcequivalent to the sum of the widths of the ends of the arms. For thedual purpose of spacing the conductive members 66 apart and forestablishing a resilient or lost-motion connection between theconductive member 66 and the spring tensioning members 68, 69, anarcuate member I2 is placed between the inner face of the conductivemember adjacent the edges of said members. This arcuate member 12 isriveted fixedly in position by means of rivets passing through theconductive members and the arcuate member. In a diametrically oppositeposition, a member 74 is placed between the conductive members 66. Inthickness, this operating member 74 is the same as member 12 and inshape it is somewhat similar to the member 12 with the exception that aradial extension protrudes outwardly from beyond the edges of theconductive member 66 in position to be engaged by portions of manualactuating members, hereinafter to be described.

' When the movable contact structure is assembled, it will comprise aunit capable of mounting upon the square section of the main operatingshaft 40 of the device, so that the spring tension members 68 and 69will turn as a unit with the shaft. Since the outturned ends of thespring 18 embrace the arms 68a, 69a of th spring tensioning members andthe spacing member 12, and since the latter is Permanently connectedwith the conductive members 66, the whole movable contact structure willnormally turn as a unit with the shaft. As the shaft turnscounterclockwise from the position shown in Fig. 8 under the influenceof the electromagnetic cperating means, the contacts 62 and 64 will bebridged; in like manner, when the electromagnetic means is deenergizedand the shaft rotates clockwise, the contacts 62 and 64 will bedisengaged by the bridging contacts.

In order to cause engagement or disengagement of the bridging contactwith the fixcd-contacts 62 and 64 by manual operation when conditions sorequire, regardless of the condition of the electromagnetic operatingmeans, there are provided circuit making and circuit breaking thumbmembers 80 and 82 plvotally mounted upon the mounting rods 36 and 31.These thumboperated members 80 and 82 may conveniently be molded frominsulating material in the form illustrated in Figs. 3 and 8. Preferablythey will be formed with a generally curved or circular formation, suchas 800, at one end, through which is bored a circular hole for thereception of the mounting rods 36 and 31. From this portion extends awinged or thumb-engaging portion 6flt which protrudes through and beyondthe edge of the insulating disc 60, so that at the exterior of thedevice it will be engageable for manipulation by one's thumb orforefinger. For engaging and moving the movable contact structure,extensions 86a, 82a, from portions 800, 820, are directed inwardly ofthe device into the path of movement of the radial extensions 14a of thecontact structure and are so placed as to be engageable with oppositesides of that radial extension. To permit depression of the thumb piecesand 82, the mounting disc 60 is provided with recesses, such as 60a.

Referring to Fig. 8, with the parts in the position there shown, if thethumb piece 80 be depressed, the extension 8lla will engage the radialextension "a to rotate it counterclockwise, thereby causing the movablecontact member 66, which is fixed to part 14, to rotate counterclockwiseand to engage the fixed contact. During such movement, the main shaft ofthe device, and thus the spring tensioning members 68 and 69 affixedthereto, would normally remain stationary. Thus, one end of the coilspring 10 will be held stationary by reason of its engagement with thearm of the spring tensioning members 68 and 69. The other end of thespring, however, would be moved by reason of the engagement therewith ofthe arcuate member 12 moving with the conductive member 66. Because thespring is relatively weak as compared with the friction and inertia ofthe shaft 40 and the parts it carries, the tension of the spring doesnot cause the shaft to move.

If the auxiliary switch (comprised of contacts 62, 64, 66) be connectedin the holding circuit of the electromagnetic operating means in shuntwith the usual start switch (not shown), it will be obvious that as soonas the contacts 62, 64 are bridged, the electromagnet will be energized,thus causing the main shaft of the device to rotate counterclockwisefollowing the partially-completed counterclockwise rotation of thebridging member 66 and completing that counterclockwise motion to holdthe bridging contact in engagement with the stationary contact andthereby maintaining the device in closed circuit position.

An opposite result may be obtained by pressing the thumb piece 82 whenthe device is in closed circuit position. In that position, the radialextension 14a will lie adjacent the upward extension 82a of the thumbpiece; and depressing the thumb piece 82 will rotate the movable contact66 in clockwise direction, disengaging it from the stationary contacts.This rotation of the movable contact member will take place without thenecessity of any movement of the main shaft. As soon as the holdingcircuit is broken, the device will be free to resume open circuitposition under the force of the return spring 10, as hereinbeforedescribed. Thus, the auxiliary switch 62, 64, 66 performs the functionsof the usual holding or sealing in contacts but in addition it canfunction as a local control switch for both opening and closingelectromagnetically-operated main contacts.

The line contactors and their operation There are three sets of powerline contactors, each set including a pair of fixed contacts and abridging contact member for engaging the fixed contacts. When used in athree-line power system, one set of contacts will be employed for eachof the power lines. Each contactor is housed in a separate section (C, Dor E), the housing for each section comprising a s acing disc I and amounting disc I02, H2 or I22. On the latter are mounted the fixedcurrent carrying parts. The discs may be of molded insulation suitablyrecessed and apertured for the fixed contacts, the movable contactstructure and the mounting and terminal rods.

In the section C is the ccntactor for the neutral line. This section ismade up of molded insulation discs I08, I02. The fixed contact membersfor this set are identical in structure and comprise stamped sheet metalpieces I00 of irregular shape, as indicated in Fig. 3. mounted upon themounting disc I02 by means of screw bolts. The members I00 have a flatcentral portion lying in a radial recess adjacent the periphery of thedisc I02. A portion I00a of the members I00 extends radially inward intoa circular recess molded into the face of the disc, within which recessthe movable contact member I04' may oscillate. Welded transversely ontothe edge of the inwardly-extending portions of the members I00 arerectangular contact blocks I000 of good contact material, such assilver, positioned so as to be engaged and disengaged by similar contactblocks I04c on the end of the arms I04b of the movable contact. Thefixed contact members I00 may have an outwardly-extending terminalportion I00b which may be twisted at right angles to the central portionof the members I00.

The rotatable contact member I04 comprises a stamped sheet metal memberI04a having a large central portion with a pair of counterbalancing armsI041) extending in diametrically opposite directions. To the ends of thearms I04b the contact tips I040 are permanently afiixed.

For the purpose of maintaining the circuit in case of momentarydisengagement of contact blocks I000 and I000, dual supplementarycontact members IOS stamped from sheet metal and lying against oppositefaces of the central member may be provided. Arcuate fingers I06aconforming substantially to the curvaure of a radius about the axis ofthe movable contact may he provided on opposite sides of the maincentral portion in diametrically opposite positions so as to engage anddisengage the inwardly-extending end I00a of the fixed contact membersI00.

In order that these circuit maintaining sup plomentary contacts I05shall engage their stationary counterparts after the butt-contact tipsI04c engage the stationary contact blocks I000 and disengage before thecontacts I040 separate from the contacts I000, the center I04a of thecontact member I04 is provided with four equally-spaced,concentrically-placed, arcuate key hole slots I04s, through each ofwhich passes one of four pins I061) that join the pair of supplementarcontacts I06 by means of peened-over ends of said pins. The enlargementof the ends of the slots I04s around the pins I06p provides limitedrelative motion between the pins and the contact I04 to take care ofmanufacturing inaccuracies and to insure proper contact engagement. Lyinin said slots I04s and pressin at one end against one end of the slotand at the otherend against the pins I061) are small coiled compressionsprings I01, the springs being held in said slots by theadjacently-lying surfaces of.

the mid-portion of the contact members I06.

The supplementary contacts I06 and the main contacts I04 are sodimensioned that, in the disengaged or open-circuit condition, theangular distance between supplementary contacts IBM 10 and I06 isgreater than the angular distance tween the butt contacts I 000 andI04c. Thus the butt contacts will engage first.

Since the supplementary contacts I06 turn with the shaft 40 by reason ofthe non-circular connection with the shaft 40, the supplementarycontacts will be positively moved to disengage the fixed contact membersand will do so while the butt contacts I040 are still maintained inengagement with contacts I000 by the action of the springs I01. S ncethe butt contact I040 will engage first and disengage last, thesupplementary contacts will normally only be called on to maintain thecircuit in case of any tendency of the butt contacts to separate. Thedescribed structure, thus, maintains continuously the closed-circuitrelation of the fixed and movable contact structures, considered as awhole, by reason of the engagement of contacts I06a and I00c. so long asthe shaft 40 remains unmoved, even though vibration or other causesmight tend momentarily to separate the butt contacts I04c, I00c.

Against the outside surfaces of the supplementary contact members I06metal driving discs I09 are placed; and all of these parts are thensecured together to form a permanent dynamically and statically balancedunit. A square aperture is formed in each of the parts, except themember I04a which has a large circular aperture, for the reception ofthe main shaft of the device, so that the movable contact unit will movewith the main shaft as it oscillates.

When the spacing disc I08 and the mounting disc I02 are placed face toface with their recesses adjacent, the movable current carrying partsare enclosed and are insulated from the parts within the sections B andD.

The movable contacts within the sections D and E are or may be identicalwith that within the section C.

The stationary contacts in sections D and E may be identical with thosein section B. However, when it is desired to use overload protection inconnection with these devices, one of the contacts IOI in each of thesesections D and E need not have an outside terminal portion. Suchcontacts may be connected to the overload heater coil in the section Fby bolts I I6, I I8 which perform the functions of a securing means anda connector. These bolts may pass through registerin apertures, such asII 2a, I 22a, near the periphery of the mounting discs H2, I22 and thespacing discs I08. For connection with the bolt ends, an arcuateextension or arm IOIe may be formed upon the contact members IM to liewithin recesses of similar shape (such as N21, for example) molded inthe discs II2, I22 adjacent their peripheries. The end of such arcuateextension I0 Ie is enlarged and apertured with the aperture inregisterwith the apertures II7a, I22a in the discs II2, I22. By having theextension IOIe embedded within and flush with the surface of the discsII2, I 22, it is possible to have the spacing discs lie flat against thesurface of the discs II2, I22, and at the same time to substantiallyenclose the current carrying parts.

The overload protective devices 7 tent in the protective end of thedevice is the need to prevent actuation, when shocks occur, for unlessthe overload or protective devices be shockproof, they may operate undershock conditions to trip the breaker open in spite of all precautionstaken in making the breaker itself shockproof.

The overload protective devices themselves are mounted upon a moldedinsulation mounting disc I30 which is suitably and symmetricallyrecessed at various points and places on each side of a vertical axis ofsymmetry for the individual elements which make up the dual protectivedevices.

On one side of the mounting disc I30 are mounted the heater coils andbimetallic strips (see Figs. 15 and 16); on the other side (see Figs. 20and 21) is mounted the balanced tripping mechanism which controls arotary switch connectible in the electromagnetic circuit so as toaccomplish deenergization of the magnet and resultant circuit openingmovement of the whole device on overload. The tripping mechanism is aremovable unit (see Fig. 22 wherein it is removed) which can be trippedby the action of bimetallic strips I44 and I45 responsive to heatdeveloped on overload in resistance wire coils I32, I34 carrying mainline current and placed next to the bimetallic strips.

Outside connections to the heater coils are made through identicalstamped sheet metal terminal members I35, I38 mounted in diametricallyopposite radially directed recesses at the periphery of the mountingdisc I30 having their terminal portions, such as I38a, extending beyond.To accommodate the heater coils and bimetal members. oblique channelsI33, I35 convergent from the inner ends of the terminal members I38, I38are formed in the mounting disc. At the inner ends of these channels.L-shaped stamped sheet metal connectors I40, I42 form a. mounting towhich one end of the heater coils is secured, their opposite ends beingscrewed to the terminals I38, I38, whereby the coils are positioned inthe upper part of the channels.

Electric connection of the heaters I32, I34 to the main contactextensions IOIe of the sections D and E respectively is by the connectinbolts I I8, "-8 respectively, insulating sleeves II8s and Has beingplaced around the shanks of the bolts to insure insulation of the boltsfrom other parts of sections through which they may pass. Boltreceivingapertures I30b are formed in the disc I30 in register with aperturesII2a. I 22a in sections D and E for the bolts H8 and H8.

Located beneath. and substantially parallel to the axis of the heatersI32, I34 are bimetal strips I44, I46 mounted at one end of smallbrackets I43, I45. The brackets are each secured at one end to themounting disc I30 by through bolts I41.

To adjust the bimetal strips one end of the bimetal supporting bracketsI43 receives a screw bolt I50, which is bored through and internallythreaded to receive a calibration-compensating screw I52 that engagesone end of a lever I 54 pivotally mounted near one end in the disc I30.The other end of the lever engages the under surface of the bimetal sothat on turning the adjustment bolt and screw the lever is rocked tovary the position of the bimetal with resultant variation in the amountof flexure thereof that will cause the latch I88 to trip free of thelatch disc 200. Suitable locking means, as shown, are

12 provided to maintain the position of adjustment of the screw I52 andbolt I50.

In order that the bimetal strips may act on the tripping mechanism onthe opposite side of the mounting disc I30, the disc is pierced withopenings I30a (Figs. 21 and 16) beneath the free ends of the bimetalstrips at the end of the channels I33, I35, where the connectors I40,I42 are. As the bimetal strips flex on overload, their ends (one orboth) enter the openings I30a to engage buttons I98 on the triggermember of the tripping mechanism now to be described.

The tripping mechanism is carried by a frame that may be stamped fromsheet metal in the form best indicated in Fig. 23. The central portionof this frame I is in the form of a parallelogram, from the oppositecorners of which there are extensions I82, I84. The extension I82 haslateral arms or lugs I86 bent up at right angles thereto, between whichis located the dynamically and statically balanced pivoted triggermember I88 which is preferably formed from molded insulating materialinto hexagonal prismatic form. In order to resiliently maintain thetrigger member in a neutral position, obliquelyangled leaf springmembers I92, I94 each have one arm lying upon and screwed to the face ofthe frame I80, while the other arm extends obliquely upward to engageconverging adjacent faces of the trigger member I88. On the oppositeside of the trigger member from said converging faces semisphericalbuttons or nubs I98 are located near the ends of the trigger in positionto be engaged by the ends of the one or the other of the bimetallicmembers. Thus, when either of the bimetallic members bend and pressagainst either of the nubs or heads I98, the trigger member I88 will becaused to pivot. In the central portion of the trigger member is moldeda balanced tripping member which is balanced by having similar fingerssuch as I98 extending in opposite directions. The finger I98 extendsradially of the pivotal axis beyond the surface of the tripping memberin position to be engaged by the radial shoulder on a dynamicallybalanced rotary latch disc 200 which is driven onto, keyed to. orotherwise secured to, a stud shaft 202. To afford support for bearingsfor the stud shaft 202, the frame I80 has its extension I84 turned up atright angles to the central section of the frame I80 and its end againturned at right angles so as to lie parallel to the central section I80.Conical hearing holes are formed in the end of the stud shaft 202 toreceive the conical bearing member 204 located in the central portion ofthe frame I80 and to receive the conical end of a journal pin 206 whichis screw-threaded into an aperture in the arm I co-axial with theconical bearing member 204. The pin 308 may be adjusted to remove allexcess play and prevent movement under impact.

In order to bias the latch disc 200 in one direction normally, a coilspring 208 is placed around the end of the stud shaft 202 with one endof the spring 208 anchored in the frame I80, and the other anchored inthe latch disc. In order to limit the rotation of the latch disc, anarcuate recess 200a is formed adjacent the periphery thereof andextending through an angle of approximately 60 degrees. A pin I80aaflixed in the central portion of the frame I 80 extends up into theaperture 200a and acts as a stop to limit the rotation of the latch disc200.

Carried by the stud shaft 202 at its end, is a movable self-aligningcontact member made up of a pair of insulating discs 2"), between whichand to which are riveted a pair of bridging contact members 2I2 havingthe form illustrated in Fig. 23, namely a ring-shaped portion withdiametrically opposite apertures for the rivets and with contact bladesdiametrically opposite each other but spaced 90 degrees from the rivetholes. An insulating spacer disc 2 is placed between the two bridgingcontact members, so that the blades of the members may engage oppositesides of fixed contact fingers 2I6a (see Figs. 8 and 19). These fingers2I8a extend radially inward as extensions from contact and terminalmembers 2IG that may conveniently be stamped from highly conductivesheet metal into the oblique form shown in Fig. 15. The members 2I6 arebolted to the mounting disc I30 in symmetrical positions of the axis ofsymmetry on opposite sides. Recesses having the same form and shape asthe members 2I8 are provided for embedd ng said members in the base ofthe mounting disc I28. The outer ends of the members 2 l6 are bent toprovide terminal lugs, which are provided with terminal screws inconventional fashion.

In order to reset the thermal-overload opened contacts 2I2 into positionto bridge the contacts 2I5a, there is provided a resetting button in theform of a depressible insulating bar I60 sliding in a rectilineartangential passage I62 in the d'sc I30. A spring I84 in the bottom ofpassage I62 urges the button outwardly of the passage; and a laterallyextending arm I 56 near the inner end of the button is positioned toengage a pin I68 extending up from the surface of the latch disc 288.When the button is depressed, the engagement of arm and pin causerotation of the latch disc 280 against the urge of spring 288 until thetongue I98 falls back of the shoulder on the latch disc to hold saiddisc latched. In that position the contacts 2 I2 and 2 I6 are engaged.

From the foregoing description of the parts, it may be observed thatwhen either one or the other of the heater coils becomes overheated byexcess current, it will cause one or the other of the bimetallic membersto bend, so that its end engages and turns the trigger member I88,causing its tongue Or extension I98 to disengage the shoulder on thelatch disc 280 (the positioning springs I92 and I94 for maintaining thelatch ng member I88 in neutral position ar not of sufficient strength tointerfere with the overload operation of the bimetallic member). As soonas the latch disc 208 is free, the spring 208 will cau e it to rotate.Since the stud shaft 202 turns with the latch disc, the movable contactstructure will also turn with it and the bridging contact member 2 I 2thereof will thereupon disengage the fixed contact members to break thecontrol circuit. In conventional practice, the contacts controlled bythis tripping mechanism will be in the holding circuit of theelectromagnet and their disengagement will cause the energization of theelectromagnet coil, whereupon under the influence of the biasing springthe electromagnet conta ts and the shaft on which they are mounted wllrotate into open circuit position, causing the switch to open.

The dynamic balance of movable parts is carried out in the overloaddevices by the-structure of the trigger i88 with itsoppositely-extending mutually balancing fingers I98 and the springs I92,I94 which balance it in latching position, and in the balanced rotarycontact structure 2I0, 2I2 2 in which, also,'the stationary contacts areengaged on both sides so as to prevent momentary disengagement due toshock occurring in an axial direction.

In Fig. 24 there is shown diagrammatically one possible method ofconnecting the form of invention illustrated in the preceding figures.In this diagram like reference characters indicate equivalent physicalparts of the device illustrated in the preceding figures. illustratesone form of connections, the invention in no sense is limited thereto.

In considering the functions, advantages and novel features, thefollowing should be noted:

Long angular rotation of the armature is one of the factors desirablefor securing a high interrupting gap of th contacts for direct currentratings, without resorting to condensers or blow out coils. In thepresent invention, the air gap of the armature can be regulated to anyintermediate position, to suit various interrupting characteristics, bygoverning the location of the stop-plate lugs 44a. On maximum stroke,the armature moves within that portion of the solenoid that produces themaximum constant magnetic force value, with a minimum of inrush current.

Due to the high starting torque resulting from the novel magnetconstruction, the armature return spring may be of sufficient strengthto arrange the same contacts in normally closed position if required,such as by reversing the fixed and bridging contacts and plac ng thebridging contact degrees from its present position on the main shaft.The contacts will then face oppositely from the present showin and willbe normallv engaged. This reversal will not interfere with the d namicand static balance or condit on of eouilibrium of the device, since allthe movable parts are individually balanced.

Being totally enclosed, the movable parts are protected aga n ttampering, atmospheric conditions, and the like.

From the foregoing it will be observed that all mo able part are inbalanced condition, in both open and clo ed po itions. Since the returnspring 2 which normally would move the parts to open position, isovercome by the electromagnet while the latter is energized there is notendency by weight, bias, or location of the movable parts to move whenthe whole device is suddenly subjected to shock or violent motion. Thebalance of the parts and condition of equilihrium avoids such tendency.At the same time it prov de a more ea ily operable device. requiring les power with better holding qualifications.

Many modifications within the scope of the invention will occur to tho eskilled in the art. Therefore I do not limit the invention to theembodiment disclosed.

I cla m:

1. In an electromagnetic switch, a rotary arma ure ha ingcounterbalancing oppo itely extending arms, a shaft actuated by saidarmature, oppo ite electromagnet coils acting on said armature solidinflexible movable contact means mounted on said shaft, rigid fixedcontact means engageable by said movable contact means, said movablecontact means having counterbalancing ort ons to maintain static anddynamic equilibrium and to avoid tendency to move from a given po itionwhen the switch is subjected to shock or motion, and a plurality ofcoiled springs between said shaft and said movable contact means topermit limited motion of said shaft Although the diagram afterengagement of said fixed and movable contact means.

2. In an electromagnetic switch, a rotary armature havingcounterbalancing oppositely extending arms, a shaft actuated by saidarmature, opposite electromagnet coils acting on said armature, a solidinflexible movable contact member mounted on said shaft, solidinflexible fixed contact means engageable by said movable contact means,said movable contact member having counterbalancing portions to maintainstatic and dynamic equilibrium and to avoid tendency to move from agiven position when the switch is subjected to shock or motion, andmeans including a plurality of independent spring members to resilientlymount said solid inflexible movable contact means on said shaftpermitting limited motion of said shaft after engagement of said contactmeans.

3. In an electromagnetic switch, a rotary armature havingcounterbalancing oppositely extending arms, a shaft actuated by saidarmature, opposite electromagnet coils acting on said armature, rigidmovable contact means mounted on said shaft, rigid fixed contact meansengageable by said movable contact means, said movable contact meanshaving counterbalancing portions to maintain static and dynamicequilibrium and to avoid tendency to move from a given position when theswitch is subjected to shock or motion, said fixed contact means haltingsaid rigid movable contact means on engagement thereof, and means toresiliently mount said movable contact means on said shaft permittinglimited motion of said shaft after engagement of said contact means.

4. In an electromagnetic switch, a rotary armature, a shaft actuated bysaid armature, electromagnet coils to actuate said armature, contactmeans moved by said shaft, fixed contact means 'engageable by saidmovable contact means, a non-rigid connection between said shaft andmovable contact means permitting movement of said contact means relativeto said shaft, manually operable means to move said movable contactmeans into or out of engagement with said fixed contact means regardlessof the condition of energization or deenergization of the electromagnet.

5. In an electromagnetic switch, a rotary armature, a shaft actuated bysaid armature, electromagnet coils to actuate said armature, fixedcontact means, movable contact means on said shaft engageable with saidfixed contact means, means resiliently connecting said shaft and movablecontact means and permitting movement of said movable contact meansindependently of said shaft. manually actuated means for moving saidmovable contact means independently of said shaft.

6. In an' electromagnetic switch, a rotary armature, electromagnet coilsto actuate said armature, a shaft actuated by said armature, controlcontact means moved by said shaft and nonrigidly mounted thereon, fixedcontact means engageable by said movable contact means, main contactmeans movable by said shaft, main fixed contact means engageable by saidmain movable contacts, manually actuated means for moving said movablecontrol contact means without moving said shaft.

7. In an electromagnetic switch, a rotary armature, electroma-gnet coilsto actuate said armature, a shaft actuated by said armature, controlcontact means moved by said shaft and nonrigidly mounted thereon, fixedcontact means engageable by said movable contact means, connecting meansbetween said fixed and movable contact means and said coils forcontrolling the energization of said coils, main contact means movableby said shaft, main fixed contact means engageable by said main movablecontacts, manually actuated means for moving said movable controlcontact means without moving said shaft to cause energization ordeenergization of said coils.

8. In an electromagnetic switch, a rotary armature, electromagnet coilsto actuate said armature, a shaft actuated by said armature, controlcontact means moved by said shaft and nonrigidly mounted thereon, fixedcontact means engageable by said movable contact means, connecting meansbetween said fixed and movable contact means and said coils forcontrolling said coils, main contact means movable by said shaft, mainfixed contact means engageable by said main movable contacts, manuallyactuated means for causing engagement or disengagement of said controlcontact means to cause deenergization or energization of said coils andto actuate said main contact means.

9. In an electromagnetic switch, a rotary armature, electromagnet coilsto actuate said armature, a shaft actuated by said armature, controlcontact means moved by said shaft and nonrigidly mounted thereon, fixedcontact means engageable by said movable contact means, main contactmeans movable by said shaft, main fixed contact means engageable by saidmain movable contacts, manually actuated means for moving said movablecontrol contact means without moving said shaft, each of said movablecontact means and said armature being constructed, arranged and mountedon said shaft in dynamically and statically balanced conditon to avoidtendency to move from a given position when the switch is subjected toshock or motion.

10. In an electromagnetic switch, a rotary armature, electromagnet coilsto actuate said armature, a shaft actuated by said armature, controlcontact means moved by said shaft and non-rigidy mounted thereon, fixedcontact means engageable by said movable contact means, main contactmeans movable by said shaft, main fixed contact means engageable by saidmain movable contacts, manually actuated means for moving said movablecontrol contact means without moving said shaft, each of said movablecontact means and said armature being separately mounted on said shaftand being removable therefrom and being constructed and arranged indynamically and statically balanced condition, said condition of ba'ancebeing undisturbed by removal of any of said contact means.

11. An electromagnetic switch comprising plural separate sections,cooperating insulating discs forming certain of said sections andhousing separate sets of contact means, a shaft passing through saidsections, rotary contact means within said contact housing sectionsconnected and moved by said shaft, and fixed contact means engaged bysaid rotary contact means, rotary electromagnetic operating mechanism inone of said plural sections for moving said shaft comprising an armatureon said shaft, and plural toroidal coils for actuating said armature.

12. An electromagnetic switch comprising plural separate sections,cooperating insulating discs forming certain of said sections and housi7ing separate sets of contact means, a shaft passing through saidsections, rotary contact means within said contact housing sectionsconnected and moved by said shaft, and fixed contact means engaged bysaid rotary contact means, rotary electromagnetic operating mechanism inone of said plural sections for moving said shaft comprising an armatureon said shaft, and plural toroidal coils for actuating said armature,said movable contact means and said armature being constructed andmounted on said shaft in individual and combined dynamic and staticbalance to avoid tendency to move from a given position when said switchis subjected to shock or motion.

13. In an electromagnetic switch, a rotary armature, electromagnet coilsto actuate said armature, a shaft actuated by said armature, controlcontact means moved by said shaft and non-rigidly mounted thereon, fixedcontact means engageable by said movable contact means, main contactmeans movable by said shaft, main fixed contact means engageable by saidmain movable contacts, means normally urging said shaft into a certainposition, said urging means being overcome by energization of said coilsand manually actuated means for moving said movable control contactmeans without moving said shaft to cause energization of said coils formoving said shaft electromagnetically, or deenergization of said coilsfor permitting said urging means to return said shaft to normalposition.

14. A rotary electromagnetically operate switch comprising a shaft, anarmature mounted to turn said shaft, electromagnet coils to actuate saidarmature, movable control contact means operable by said shaft, fixedcontact means engageable by said movable control contact means, movablemain contact means operable by said shaft, fixed main contact meansengageable by said movable main contact means, means normally urgingsaid shaft into one position when said coils are deenergized, meansconnecting said movable control contact means to said shaft permittingrelative motion by the control contact means while the shaft remainsstationary, manual actuating means for moving said movable controlcontact means to deenergize the coils to permit return of said shaft tonormal position by said urging means, or to energize the coils toovercome the urging means and move said shaft to energized position,said connecting means and shaft and electromagnet cooperating to causesaid control contact means to remain in engaged or disengaged positionafter manual movement thereto, until subsequent opposite movement ofsaid shaft or actuation of said manual means.

15. In an electromagnetic switch, electromagnetic operating meanscomprising coils, a rotary shaft and a balanced armature on said shaft,in combination with local operating means for controlling said magnet,and main contact means operated by said shaft, said local control meanscomprising movable contact means operated by said shaft and fixedcontact means engaged thereby, manual actuating means for said localmovable contact means for causing energization or deenergization of saidmagnet, means mounting said movable local control contact means on saidshaft and causing movement of said local movable contact means with saidshaft but permitting independent movement thereof by said manualactuating means.

18. In an electromagnetic switch, electromagnetic operating meanscomprising coils, a rotary shaft and a balanced armature on said shaft,in combination with local operating means for controlling said magnet,and main contact means operated by said shaft, said local control meanscomprising movable contact means operated by said shaft and fixedcontact means engaged thereby, manual actuating means for said localmovable contact means for causing energization or deenergization of saidmagnet, means mounting said movable local control contact means on saidshaft and causing movement of said local movable contact means with saidshaft but permitting independent movement thereof by said manualactuating means, said main contact means and said movable local contactmeans having balanced moving parts for the purpose of avoiding tendencyof said shaft to move from a given position when the switch is subjectedto shock or movement.

17. An electromagnetic switch comprising a rotary armature, oppositelylocated arcuate arms on said armature, arcuate magnetic pole pieceslying outside the arc of movement of said arms but adjacent thereto,arcuate electromagnet coils oppositely located, said pole pieces lyingbetween the ends of opposite coils to form a flux path, each pole piecehaving an extension entering the end of a coil, a shaft actuated by saidarmature, a solid inflexible movable contact means mounted on saidshaft, rigid fixed contact means engageable by said movable contactmeans, said movable contact means having counterbalancing portions tomaintain static and dynamic equilibrium and to avoid tendency to movefrom a given position when the switch is subjected to shock or motion,and a plurality of coiled springs between said shaft and said movablecontact means to permit limited motion of said shaft after engagement ofsaid fixed and movable contact means.

18. An electromagnetic switch comprising a rotary armature, oppositelylocated arcuate arms on said armature, arcuate magnetic pole pieceslying outside the arc of movement of said arms but adjacent thereto,arcuate electromagnet coils oppositely located, said pole pieces lyingbetween the ends of opposite coils to form a flux path, each pole piecehaving an extension entering the end of a coil, a shaft actuated by saidarmature, contact means moved by said shaft, fixed contact moansengageable by said movable contact means, a non-rigid connection betweensaid shaft and movable contact means permitting movement of said contactmeans relative to said shaft, manually operable means to move saidmovable contact means into or out of engagement with said fixed contactmeans regardless of the condition of energization or deenergization ofthe electromagnet.

19. An electromagnetic switch comprising a rotary armature, oppositelylocated arcuate arms on said armature, arcuate magnetic pole pieceslying outside the arc of movement of said arms but adjacent thereto,arcuate electromagnet coils oppositelyv located, said pole pieces lyingbetween the ends of opposite coils to form a flux path, each pole piecehaving an extension entering the end of a coil, a shaft actuated by saidarmature, control contact means moved by said shaft and non-rigidlymounted thereon, fixed contact means engageable by' said movable contactmeans, main contact means movable by said shaft, main fixed contactmeans engageable by said main movable contacts, manually actuated meansfor moving said movable control contact means without moving said shaft.

20. An electromagnetic switch comprising plural separate sections,cooperating insulating discs forming certain of said sections andhousing separate sets of contact means, a shaft passing through saidsections, rotary contact means within said contact housing sectionsmoved by said shaft, and fixed contact means engaged by said rotary.contact means, rotary electromagnetic operating mechanism comprising arotary armature, oppositely located arcuate arms on said armature,arcuate magnetic pole pieces lying outside the arc of movement of saidarms but adjacent thereto, arcuate electromagnet coils oppositelylocated, said pole pieces lying between the ends of opposite coils toform a flux path,

each pole piece having an extension entering the end of a coil.

21. An electromagnetic switch comprising a rotary armature dynamicallyand statically balanced for the purpose of avoiding a tendency to movefrom a given position when the electromagnet is subjected to shock ormotion, said armature having oppositely extending counterbalancing armswith circumferentially curved end portions, electromagnet coils havingarcuate open-end cores to receive said arms, magnetic pole piecesadjacentthe arcs of travel of said arms and positioned between the endsof opposite coils, a shaft actuated by said armature, a solid inflexiblemovable contact member mounted on said shaft, fixed contact meansengageable by said movable contact means, said movable contact memberhaving counterbalancing portions to maintain static and dynamicequilibrium and to avoid tendency to move from a given position when theswitch is subjected to shock or motion, and means including a pluralityof independent spring members to resiliently mount said solid inflexiblemovable contact means on said shaft permitting limited motion of saidshaft after engagement of said contact means.

22. An electromagnetic switch comprising a rotary armature dynamicallyand statically balanced for the purpose of avoiding a tendency to movefrom a given position when the electromagnet is subjected to shock ormotion, said armature having oppositely extending counterbalancing armswith circumferentially curved end portions, electromagnet coils havingarcuate open-end cores to receive said arms, magnetic pole piecesadjacent the arcs of travel of said arms and positioned between the endsof opposite coils, a shaft actuated by said armature, rigid movablecontact means mounted on said shaft, rigid fixed contact meansengageable by said movable contact means, said movable contact meanshaving counterbalancing portions to maintain on static and dynamicequilibrium and to avoid tendency to move from a given position when theswitch is subjected to shock or motion, said fixed contact means haltingsaid rigid movable contact means on engagement thereof, and means toresiliently mount said movable contact means on said shaft permittinglimited motion of said shaft after engagement of said contact means.

23. An electromagnetic switch comprising a rotary armature dynamicallyand statically balanced for the purpose of avoiding a tendency to movefrom a given position when the electromagnet is subjected to shock ormotion, said armature having oppositely extending counterbalancing armswith circumferentially curved end portions, electromagnet coils havingarcuate openend cores to receive said arms, magnetic pole piecesadjacent the arcs of travel of said arms and positioned between the endsof opposite coils, a shaft actuated by said armature, fixed contactmeans, movable contact means on said shaft engageable with said fixedcontact means, means resiliently connecting said shaft and movablecontact means and permitting movement of said movable contact meansindependently of said shaft, manually actuated means for moving saidmovable contact means independently of said shaft.

24. An electromagnetic switch comprising a rotary armature dynamicallyand statically balanced for the purpose of avoiding a tendency to movefrom a given position when the electromagnet is subjected to shock ormotion, said armature having oppositely extending counterbalancing armswith circumferentially curved end portions, electromagnet coils havingarcuate open-end cores to receive said arms, magnetic pole piecesadjacent the arcs of travel of said arms and positioned between the endsof opposite coils, a shaft actuated by said armature, control contactmeans moved by said shaft and nonrigidly mounted thereon, fixed contactmeans engageable by said movable contact means, main contact meansmovable by said shaft, main fixed contact means engageable by said mainmovable contacts, manually actuated means for moving said movablecontrol contact means without moving said shaft.

25. An electromagnetic switch comprising a rotary armature dynamicallyand statically balanced for the purpose of avoiding a tendency to movefrom a given position when the electromagnet is subjected to shock ormotion, said armature having oppositely extending counterbalancing armswith circumferentially curved end portions, electromagnet coils havingarcuate openend cores to receive said arms, magnetic pole piecesadjacent the arcs of travel of said arms and positioned between the endsof opposite coils, a shaft actuated by said armature, control contactmeans moved by said shaft and non-rigidly mounted thereon, fixed contactmeans engageable by said movable contact means, main contact meansmovable by said shaft, main fixed contact means engageable by said mainmovable contacts, manually actuated means for moving said movablecontrol contact means without moving said shaft, each of said movablecontact means and said armature being constructed, arranged and mountedon said shaft in dynamically and statically balanced condition to avoidtendency to move from a given position when the switch is subjected toshock or motion.

HAROLD E. SCHLEICHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 365,438 Jacobs June 28, 1887792,860 Sundh et al June 20, 1905 830,209 Conkling et a1 Sept. 4, 1906913,104 Cedergren Feb. 23, 1909 928,516 Hellmuncl July 20, 19091,222,431 McCarthy Apr. 10, 1917 1,356,290 Kellum Oct. 19, 1920 (Otherreferences on following page) UNITED STATES PATENTS Number Name DateWood Feb. 19, 1924 Tugendhat May 18, 1926 Spencer Jan. 28, 1930 AppleJune 2, 1931 Shepard Dec. 8, 1931 Bossart May 17, 1932 Getty Dec. 31,1935 Bassett May '7, 1940 Latta May 28, 1940 Kimball Dec. 17, 1940Reynolds July 8, 1941 Walker July 7, 1942 Number Name Date, WhittakerFeb. 2, 1943 May Apr. 6, 1943 Reynolds Oct. 5, 1943 Snavely Nov. 16,1943 Cramer Dec. 21, 1943 Bucklen et a1 Jan. 18, 1944 Meuer et a1 Feb.26, 1946 Kaiser Sept. 21, 1948 FOREIGN PATENTS Country Date GreatBritain Dec. 16, 1936 France Mar. 12, 1914

